I will let you know about Moody and a tie with the Gamps. I'll have to think about that.
Rabbit tends to look immature only in front of the Death Eaters. So his status as a first tier pureblood is intact in front of the society folks.
Arthur points to his grandmother (Sabina Malfoy) and his mother (Cedrella Black) as proof that the Weasleys marry well, not to mention his own bride being a Prewett. :)